1. Field of the Invention
This invention relates to firearms. Specifically, this invention is primarily a gas operated firearm which can easily be configured to fire a variety of cartridges using a variety of box magazines and belt-feeding devices. Furthermore, this invention can be configured to feed ammunition from either the top or the bottom of the firearm. Also, this invention will permit cocking of the firearm from the left side of the upper receiver with a non-reciprocating cocking handle incorporating a bolt forward assist or a reciprocating cocking handle feature while it is configured to feed from the bottom of the upper receiver. Alternative embodiments of the invention, can permit cocking of the firearm from the right side of the upper receiver.
2. Description of Related Art
Several features of this invention have been considered or used in prior firearm designs.
The H&K Model 21 and 23 series firearms are capable of firing several different cartridges, specifically 7.62 NATO, 5.56 NATO and 7.62.times.39 mm, by changing out the barrel, magazine well (or belt feed device), and bolt. However, these rifles are recoil/blow-back operated while this invention is gas operated. Furthermore, these rifles do not permit an operator to modify the operating system mass, operating system diameter, length and pressure and/or operating system travel, as does this invention. Such modifications are necessary to solve the problem of poor operating performance which occurs when a firearm is converted to shoot more than one cartridge type.
Adjustable gas systems for rifles are well known in the art. As early as the Browning BAR automatic military rifle (designed in the early 1900s), the amount of gas used to cycle the operating system could be adjusted by restricting or increasing the size of the orifice through which the gas traveled from the barrel to the gas tube to act upon the piston operating rod. Other systems allowed various amounts of gas to bleed from the gas system by allowing the operator to open or close vent holes in the gas system. Early examples of this approach include the FN Model D BAR, and the FN FAL Rifle. Unlike these approaches, this invention is not only gas operated but it has a gas operating system which can be optimized to maximize the performance of the chosen cartridge while minimizing recoil. Additionally, the cyclic rate of the fully automatic versions of the invention to be altered without sacrificing reliability.
The closest known approach for a weapon system which can be fed from the top or the bottom of the firearm, by shifting components to the other side of the receiver is the Stoner 63 and 63A Convertible Weapon System. However, unlike the Stoners, which use only the 5.56 NATO cartridge, this invention permits the use of many of the popular cartridges such as 5.56 NATO, 7.62.times.39 mm, and 5.45.times.39 mm. Additionally, the invention permits the use of existing magazines, belts and links for the aforementioned cartridges by the simple change of the magazine well or belt feed device and bolt. While the current embodiment of this invention can fire 7.62.times.39 mm and 5.45.times.39 in addition to the 5.56 NATO cartridge. Alternative, presently envisioned embodiments of this invention, will be able to use such other ammunition as 0.45 ACP, 9 mm, 0.40 S&W pistol calibers and magazines and hunting rifle cartridges ranging from 0.223 (5.56 NATO) to 0.300 Winchester Mag. using this changeable operating system and magazine well invention. Additionally, this invention can be fired from a closed-bolt, whether cartridges are fed from the top or the bottom of the receiver. This is essential for civilian use, since open bolt firing systems are not permitted, for civilian ownership, in the United States, because they are too easily converted to fire fully automatically.
Other weapons with the recoil spring located on the operating rod are the Beretta M70 and the SIG 550 series of firearms. The difference between this element of this invention and these firearms is that this invention can use operating rods, recoil springs and buffers, and gas tubes of different dimensions without modifying the receiver. Also, the action of this invention can be cycled from the left hand side of the upper receiver using a non-reciprocating cocking handle to which a forward assist mechanism can be added, or alternatively a reciprocating cocking handle can be employed from either side of the upper receiver. Further, with this invention, the operating systems length of travel, piston diameter, mass, and recoil spring force can be changed to minimize recoil and ensure reliable operation with any given cartridge. Changing these characteristics can also alter the cyclic rate in fully-automatic versions.
For general background material, the reader is directed to U.S. Pat. Nos. 2,951,424, 3,032,882, 3,035,495, 3,045,555, 3,087,270, 3,090,150, 3,198,076, 3,235,997, 3,293,986, 3,455,204, 3,500,718, 3,512,449, 3,517,586, 3,547,001, 3,566,744, 3,683,743, 3,968,750, 4,027,415, 4,213,376, 4,311,081, 4,348,938, 4,625,621, 4,790,231, 4,791,851, 4,872,391, 4,942,802, 5,024,139, 5,050,480, 5,050,481, 5,117,735, 5,370,036 and U.S. Pat. Nos. Des. 188,193 and 192,032. Other related background material can be found in Firearms Assembly 3, published by the National Rifle Association in 1987; Small Arms of the World by Edward Clinton Ezell (12.sup.th Revised Ed.), published by Stackpole Books; and Stoner 63A Weapons System Specifications, published by Cadillac Gage Company. Each of the above references is hereby incorporated by reference in its entirety for the material disclosed therein.